The invention relates to a method of producing a package wherein a depression is formed in a shrinkable sheet material by deep drawing, the article to be packaged is brought into the depression, a cover is brought over the depression, the depression is transferred into a surrounding chamber, the chamber is evacuated, the sheet material is heated to a shrinkage temperature and the depression is closed with the cover by heat-sealing. The invention further relates to a packaging apparatus for performing this method.
A method of this kind is known from the German Patent No. 23 64 565. In this method a shrinkage of the sheet material forming the depression is obtained by bringing the sheet material into complete contact with heated walls and thus heating to the shrinkage temperature. It is therefore necessary to adapt the position of the heated walls to the form of the depression in order to avoid a further stretching of the sheet material in pressing the same to the walls. Hence each wall arrangement is only suitable for a single depression size. Furthermore, the sheet material is not heated any longer after lifting from the heated walls and thus can rapidly cool down when contacting the product to be packaged, which may lead to a premature end of the shrinking procedure.
A packaging method is known from the German patent specification No. 23 60 847 wherein components surrounded by a shrinkable foil are brought into an autoclave and steam is admitted thereto, wherein the foils are covered with clothes. Due to the steam temperature of more than 100.degree. C. the foils are heated to a softening temperature. Furthermore a controlled heating to a predetermined final temperature is not possible in this way.